Input: define separate EVIOCGKEYCODE_V2/EVIOCSKEYCODE_V2

The desire to keep old names for the EVIOCGKEYCODE/EVIOCSKEYCODE while
extending them to support large scancodes was a mistake. While we tried
to keep ABI intact (and we succeeded in doing that, programs compiled
on older kernels will work on newer ones) there is still a problem with
recompiling existing software with newer kernel headers.

New kernel headers will supply updated ioctl numbers and kernel will
expect that userspace will use struct input_keymap_entry to set and
retrieve keymap data. But since the names of ioctls are still the same
userspace will happily compile even if not adjusted to make use of the
new structure and will start miraculously fail in the field.

To avoid this issue let's revert EVIOCGKEYCODE/EVIOCSKEYCODE definitions
and add EVIOCGKEYCODE_V2/EVIOCSKEYCODE_V2 so that userspace can explicitly
select the style of ioctls it wants to employ.

Reviewed-by: Henrik Rydberg <[e-mail]>
Acked-by: Jarod Wilson <[e-mail]>
Acked-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/evdev.c

···
 }
 #undef OLD_KEY_MAX
 
-static int evdev_handle_get_keycode(struct input_dev *dev,
-				    void __user *p, size_t size)
+static int evdev_handle_get_keycode(struct input_dev *dev, void __user *p)
+{
+	struct input_keymap_entry ke = {
+		.len	= sizeof(unsigned int),
+		.flags	= 0,
+	};
+	int __user *ip = (int __user *)p;
+	int error;
+
+	/* legacy case */
+	if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))
+		return -EFAULT;
+
+	error = input_get_keycode(dev, &ke);
+	if (error)
+		return error;
+
+	if (put_user(ke.keycode, ip + 1))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int evdev_handle_get_keycode_v2(struct input_dev *dev, void __user *p)
 {
 	struct input_keymap_entry ke;
 	int error;
 
-	memset(&ke, 0, sizeof(ke));
+	if (copy_from_user(&ke, p, sizeof(ke)))
+		return -EFAULT;
 
-	if (size == sizeof(unsigned int[2])) {
-		/* legacy case */
-		int __user *ip = (int __user *)p;
+	error = input_get_keycode(dev, &ke);
+	if (error)
+		return error;
 
-		if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))
-			return -EFAULT;
+	if (copy_to_user(p, &ke, sizeof(ke)))
+		return -EFAULT;
 
-		ke.len = sizeof(unsigned int);
-		ke.flags = 0;
-
-		error = input_get_keycode(dev, &ke);
-		if (error)
-			return error;
-
-		if (put_user(ke.keycode, ip + 1))
-			return -EFAULT;
-
-	} else {
-		size = min(size, sizeof(ke));
-
-		if (copy_from_user(&ke, p, size))
-			return -EFAULT;
-
-		error = input_get_keycode(dev, &ke);
-		if (error)
-			return error;
-
-		if (copy_to_user(p, &ke, size))
-			return -EFAULT;
-	}
 	return 0;
 }
 
-static int evdev_handle_set_keycode(struct input_dev *dev,
-				    void __user *p, size_t size)
+static int evdev_handle_set_keycode(struct input_dev *dev, void __user *p)
+{
+	struct input_keymap_entry ke = {
+		.len	= sizeof(unsigned int),
+		.flags	= 0,
+	};
+	int __user *ip = (int __user *)p;
+
+	if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))
+		return -EFAULT;
+
+	if (get_user(ke.keycode, ip + 1))
+		return -EFAULT;
+
+	return input_set_keycode(dev, &ke);
+}
+
+static int evdev_handle_set_keycode_v2(struct input_dev *dev, void __user *p)
 {
 	struct input_keymap_entry ke;
 
-	memset(&ke, 0, sizeof(ke));
+	if (copy_from_user(&ke, p, sizeof(ke)))
+		return -EFAULT;
 
-	if (size == sizeof(unsigned int[2])) {
-		/* legacy case */
-		int __user *ip = (int __user *)p;
-
-		if (copy_from_user(ke.scancode, p, sizeof(unsigned int)))
-			return -EFAULT;
-
-		if (get_user(ke.keycode, ip + 1))
-			return -EFAULT;
-
-		ke.len = sizeof(unsigned int);
-		ke.flags = 0;
-
-	} else {
-		size = min(size, sizeof(ke));
-
-		if (copy_from_user(&ke, p, size))
-			return -EFAULT;
-
-		if (ke.len > sizeof(ke.scancode))
-			return -EINVAL;
-	}
+	if (ke.len > sizeof(ke.scancode))
+		return -EINVAL;
 
 	return input_set_keycode(dev, &ke);
 }
···
 			return evdev_grab(evdev, client);
 		else
 			return evdev_ungrab(evdev, client);
+
+	case EVIOCGKEYCODE:
+		return evdev_handle_get_keycode(dev, p);
+
+	case EVIOCSKEYCODE:
+		return evdev_handle_set_keycode(dev, p);
+
+	case EVIOCGKEYCODE_V2:
+		return evdev_handle_get_keycode_v2(dev, p);
+
+	case EVIOCSKEYCODE_V2:
+		return evdev_handle_set_keycode_v2(dev, p);
 	}
 
 	size = _IOC_SIZE(cmd);
···
 			return -EFAULT;
 
 		return error;
-
-	case EVIOC_MASK_SIZE(EVIOCGKEYCODE):
-		return evdev_handle_get_keycode(dev, p, size);
-
-	case EVIOC_MASK_SIZE(EVIOCSKEYCODE):
-		return evdev_handle_set_keycode(dev, p, size);
 	}
 
 	/* Multi-number variable-length handlers */

include/linux/input.h

···
 #define EVIOCGREP		_IOR('E', 0x03, unsigned int[2])	/* get repeat settings */
 #define EVIOCSREP		_IOW('E', 0x03, unsigned int[2])	/* set repeat settings */
 
-#define EVIOCGKEYCODE		_IOR('E', 0x04, struct input_keymap_entry)	/* get keycode */
-#define EVIOCSKEYCODE		_IOW('E', 0x04, struct input_keymap_entry)	/* set keycode */
+#define EVIOCGKEYCODE		_IOR('E', 0x04, unsigned int[2])        /* get keycode */
+#define EVIOCGKEYCODE_V2	_IOR('E', 0x04, struct input_keymap_entry)
+#define EVIOCSKEYCODE		_IOW('E', 0x04, unsigned int[2])        /* set keycode */
+#define EVIOCSKEYCODE_V2	_IOW('E', 0x04, struct input_keymap_entry)
 
 #define EVIOCGNAME(len)		_IOC(_IOC_READ, 'E', 0x06, len)		/* get device name */
 #define EVIOCGPHYS(len)		_IOC(_IOC_READ, 'E', 0x07, len)		/* get physical location */